I'm new to this site aswell as reloading. Today I fired my first reloads using the load tuning method descirbed on the site, worked like a charm! As for my problem, when I load the rounds in the bolt requires a rather large amount of force to close, opening is easy, i loaded Sierra 168grain matchkings over reloader 15 and wolf magnum primers. OAL was 2.805" my manual said minimum is 2.8" so I don't think they're too long. Any ideas what could have caused this would be much appreciated.

Do you use a neck sizer or a full length sizer ?
Using the full length sizer, crank that die into the press frame 1/2 turn more so it will reset the cartridge shoulder back and try the ammo in the rifle not to shoot, just for size.

You could also measure the shoulder diameter of a fired case vs. a handloaded one that is hard to chamber.

Can you use a NS die. The answer is no, that is why it is called a NS die.

You are going to have to use a FL size die or Redding body bump die to bump the shoulders back!

Too many people get hung up on NS only thinking it is the miracle accuracy cure when it is not. Over half the short range BR shooters use FL dies, 95% of the LR BR shooters FL size at least every 3 times fired in not every time. Hint Hint That should put it into perspective there.

A properly adjusted FL die only minimally sizes the sides and if set right you can bump the shoulder back .002 and have perfect loading and cases that are close to chamber dimension s.